Pieces of jewellery of annular shape that comprise a mobile part are already known. In particular, U.S. Pat. Nos. 1,830,929 and 1,936,604 both disclose a finger ring that includes concentric rings of different diameters. These rings are assembled to each other via two pivots diametrically arranged opposite each other. These pivots are provided to allow the rings to pivot relative to each other between a tilted position, in which the outer surface of the smallest ring is visible, and a nesting position, in which the largest ring covers and conceals the outer surface of the smallest ring. These two finger rings are both further fitted with fastening means provided for holding them in the nesting position.
The pieces of jewellery disclosed in these first two prior art documents are not intended to be worn in the tilted position, or in other words, the open position. Even if the wearer of such a piece of jewellery decides to wear it in the open position, the piece of jewellery must be expected to close again, at least partially, very soon. Indeed, no means is provided for preventing this movement of the mobile part. Yet, it seems desirable to offer the wearer of a piece of jewellery provided with a mobile part, the possibility of wearing the same in several different positions if he so desires.
French Patent No. 2,715,806 discloses an annular shaped piece of jewellery which is intended to be worn in two different positions. This piece of jewellery comprises an annular shaped inner part and an outer part in the shape of a ring portion. The two parts are assembled by two coaxial pivots, arranged to allow the outer part to pivot. The piece of jewellery further comprises an elastic element, secured to one of the parts, and arranged for cooperating in abutment inside one or other of two housings made in the other part. This arrangement allows the outer part to be maintained selectively in a first position, wherein the two parts are fitted one inside the other, or in a second position wherein they are tilted.
The piece of jewellery disclosed in this third prior art document has certain drawbacks. Indeed, in order for the elastic element to have the possibility of cooperating in abutment inside a housing of the other part, the document teaches that the inner part and the outer part have to remain at least partially superposed. In such conditions, the width of the outer surface of the inner part is never entirely visible. Moreover, using a deformable element secured to one of the parts, capable of being compressed between the two parts, makes the piece of jewellery relatively complex to make.